Immuno - Immune Responses (Immunity Basics)

Question 1

What is anergy? Which cells does it affect, why, and how?

Answer 1

T cells become nonreactive without costimulatory molecule. B cells also become anergic, but tolerance is less complete than in T cells.

Question 2

What are examples of bacterial toxin superantigens? By what mechanism do they act, and what effect(s) do they have?

Answer 2

Superantigens (S. pyogens and S. aureus) – cross-link the Beta region of the T-cell receptor to the MHC class II on APC’s. Can activate any T cell, leading to massive release of cytokines.

Question 3

Which bacteria have endotoxins/lipopolysaccharide? What is its mechanism, and which cells are not involved?

Answer 3

Endotoxins/lipopolysaccharide (gram-negative bacteria) – directly stimulate macrophages by binding to endotoxin receptor CD14; Th cells are not involved.

Question 4

What are 3 classic examples of antigen variation in bacteria?

Answer 4

Bacteria – (1) Salmonella (2 flagellar variants) (2) Borrelia (relapsing fever) (3) Neisseria gonorrhoeae (pilus protein)

Question 5

What is a classic example of antigen variation in viruses?

Answer 5

Influenza (major = shift, minor = drift)

Question 6

What is a classic example of antigen variation in parasites?

Answer 6

Trypanosomes (programmed rearrangement)

Question 7

In general, what are2 mechanisms for antigen variation?

Answer 7

Some mechanisms for variation include (1) DNA rearrangement and (2) RNA segment reassortment (e.g., influenza major shift)

Question 8

What is the means of acquisition for passive versus active immunity?

Answer 8

PASSIVE - Receiving preformed antibodies; ACTIVE - Exposure to foreign antigens

Question 9

What is the onset like for passive versus active immunity?

Answer 9

PASSIVE - Rapid; ACTIVE - Slow

Question 10

What is the duration for passive versus active immunity?

Answer 10

PASSIVE - Short span of antibodies (half-life = 3 weeks); ACTIVE - Long-lasting protection (memory)

Question 11

What are 4 examples of passive immunity?

Answer 11

(1) IgA in breast milk (2) Antitoxin (3) Humanized monoclonal antibody (4) Maternal IgG crossing placental

Question 12

What are 3 examples of active immunity?

Answer 12

(1) Natural infection (2) Vaccines (3) Toxoid

Question 13

After exposure to what 4 pathogens/toxins are patients given preformed antibodies (passive immunity)?

Answer 13

After exposure to (1) Tetanus toxin, (2) Botulinum toxin, (3) HBV, or (4) Rabies virus, patients are given preformed antibodies (passive); Think: “To Be Healed Rapidly”

Question 14

In which cases of pathogen/toxin exposure can combined passive and active immunizations be given?

Answer 14

Combined passive and active immunizations can be given in case of hepatitis B or rabies exposure.

Question 15

What is the purpose/goal of vaccines?

Answer 15

Vaccines are used to induce an active immune response (humoral and/or cellular) to specific pathogens

Question 16

What is a live attenuated vaccine? What kind of response does it induce?

Answer 16

Microorganism loses its pathogenicity but retains capacity for transient growth within inoculated host; Mainly induces a cellular response

Question 17

What is an inactivated or killed vaccine? What kind of response does it induce?

Answer 17

Pathogen is inactivated by heat or chemicals; maintaining epitope structure on surface antigens is important for immune response; Humoral immunity induced

Question 18

What is important for immune response due to inactivated or killed vaccines?

Answer 18

Maintaining epitope structure on surface antigens in important for immune response

Question 19

What kind of response do live attenuated versus killed/inactivated vaccines elicit?

Answer 19

LIVE ATTENUATED - Mainly induces a cellular response; INACTIVATED/KILLED - Humoral immunity induced;

Question 20

What is a pro and con of live attenuated vaccines?

Answer 20

PRO: Induces strong, often life-long immunity; CON: May revert to virulent form

Question 21

What is a pro and con of inactivated/killed vaccines?

Answer 21

PRO: Stable and safer than live vaccines; CON: Weaker immune response, booster shots usually required

Question 22

What are 7 examples of live attenuated vaccines?

Answer 22

(1) Measles (2) Mumps (3) Polio (Sabin) (4) Rubella (5) Varicella (6) Yellow fever (7) Influenza (intranasal)

Question 23

What are 5 examples of inactivated/killed vaccines?

Answer 23

(1) Cholera (2) Hepatitis A (3) Polio (Salk) (4) Rabies (5) Influenza (injection)

Question 24

What are 2 conditions with which live attenuated vaccines are often contraindicated?

Answer 24

Often contraindicated in pregnancy and immune deficiency